In the conventional micro wave ovens, a motor shaft resolves by receiving a driving power from a motor which is installed below and outside the bottom of a heating room, and this motor shaft passes through the bottom wall of the heating room in order to rotate a turn table which is installed concentrically within the heating room and at a proper height. Therefore, the micro wave which are introduced into the heating room are leaked through the through-hole formed on the bottom of the heating room, with the result that the surrounding portions of the motor are heated by the leaked micro waves, thereby causing over-heatings and malfunctions on them. Further, the micro waves which are leaked to the outside can harm humans.
In an attempt to overcome the above described problems, there has been proposed a micro wave leakage preventing apparatus which is constituted as shown in FIG. 3, and as described below. That is, a turn table 11, which is to be rotated and to mount foods within the heating room 10 (into which micro waves are supplied), receives a driving power from a motor 12 which is installed concentrically with the turn table at the outside of the heating room 10. The turn table 11 revolves by being driven by a motor shaft 12a which passes through a through-hole 10b formed on a bottom 10a of the heating room 10. A motor supporting member 13 is fitted to the motor shaft 10a and between the motor 12 and the bottom wall 10a of the heating room 10 enabling the member 13 to be disposed on the top of the motor 12. A first shielding member 14 having the shape of a funnel is disposed on the motor supporting member 13, and the lower end portion of the first shielding member 14 is fitted to the motor shaft 12a, while a dish shaped second shielding member 15 with a through-hole formed thereon is weld-fixed to the leading end of the first shielding member 13. Meanwhile the top of the second shielding member 15 is weld-fixed to the bottom 10a of the heating room 10.
In the apparatus as described above, the first shielding member 14 is installed in contact with the motor shaft 12a, and the second shielding member 15 is weld-fixed under the through-hole 10b which is formed on the bottom wall 10a of the heating room 10, as well as being weld-fixed to the first shielding member 14. Thus it becomes possible to shield up the micro waves which are leaked through the through-hole 10b of the heating room 10. However, it is impossible to suppress in a natural manner the reflection of micro waves from the first and second shielding members 14, 15, even though the heating room is sealed up. Therefore, the heat which is accumulated as the result of the reflections of the micro waves elevates the temperatures of the surrounding portions of the motor 12, thereby leaving the problem of malfunctions as before.
Meanwhile, in an attempt to overcome the conventional problems, there is proposed another micro wave leakage preventing apparatus which is disclosed in Japanese Utility Model, Laid-Open Publication No. 60-118894. In this apparatus, the turn table which mounts foods and rotates the foods within the heating room is interlocked with a motor shaft which transfers a driving power from a motor which is concentrically installed with the shaft. Further, a roller supporting member is formed on the bottom of the heating room in such a manner that the roller supporting member should be able to movably support in the radial direction a supporting roller which moves around the revolution axis of the turn table to movably support the turn table. Further, a reflecting member which moves together with the supporting roller in the radial direction in order to reflect the micro waves is fixedly secured to the supporting shaft of the supporting roller.
However, in the apparatus as described above, the supporting roller moves to the left and right by being guided by the roller supporting member which has a concavely recessed portion and a rectangular trace on the bottom of the heating room. In accordance with the movements of the supporting roller, the reflecting member moves in an interlocked manner in order to reflect micro waves, and therefore, the micro waves which are concentrated to the lower portion of the turn table can be dispersed. However, a part of micro waves is leaked through the clearance of the through-hole through which the motor shaft is inserted. Thus, the portions surrounding the motor are elavated in their temperatures, thereby causing malfunctions of the surrounding portions and fatal harms to human bodies.